Field
This disclosure is related to the field of video coding and compression. In particular, it is related to scalable video coding (SVC), including SVC for Advanced Video Coding (AVC), as well as SVC for High Efficiency Video Coding (HEVC), which is also referred to as Scalable HEVC (SHVC). It is also related to single layer coding and 3-D video coding, such as the multiview extension of HEVC, referred to as MV-HEVC. In particular, it is related to inter-component filtering and inter-layer prediction in video coding, which may also be referred to as inter-color filtering, cross-color filtering, or inter-component prediction. Various embodiments relate to systems and methods for improved inter-layer prediction signaling and related inter-component filtering processes.
Description of the Related Art
Digital video capabilities may be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, so-called “smart phones,” video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), the High Efficiency Video Coding (HEVC) standard presently under development, and extensions of such standards. The video devices may transmit, receive, encode, decode, and/or store digital video information more efficiently by implementing such video coding techniques.
Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video frame or a portion of a video frame) may be partitioned into video blocks, which may also be referred to as treeblocks, coding units (CUs) and/or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to a reference frames.
Spatial or temporal prediction results in a predictive block for a block to be coded. Residual data represents pixel differences between the original block to be coded and the predictive block. An inter-coded block is encoded according to a motion vector that points to a block of reference samples forming the predictive block, and the residual data indicating the difference between the coded block and the predictive block. An intra-coded block is encoded according to an intra-coding mode and the residual data. For further compression, the residual data may be transformed from the pixel domain to a transform domain, resulting in residual transform coefficients, which then may be quantized. The quantized transform coefficients, initially arranged in a two-dimensional array, may be scanned in order to produce a one-dimensional vector of transform coefficients, and entropy coding may be applied to achieve even more compression.
Each treeblock may further include both luma and chroma samples (e.g., pixels). Chroma subsampling is the practice of encoding pictures by providing less chroma (e.g., color) information than luma (e.g., brightness) information. Each of the luma and chroma samples in a video sequence may utilize from 8 to 14 bits. Due to the bit requirements, video encoding and decoding systems may implement various methods (e.g., intra-prediction, cross-channel prediction, inter-layer prediction, inter-component filtering) to reduce the number of bits used, and in some cases, to improve picture quality. For example, using inter-component filtering, chroma components used for inter-layer prediction may be enhanced by applying a high-pass filter to corresponding luma components. A system may determine specific filter parameters and transmit (e.g., signal, etc.), receive, and/or use them to determine luma pixels surrounding a Cb or Cr chroma pixel. This may allow such system to determine an enhanced Cb or Cr pixel, respectively. In one embodiment, signaling may include setting a flag in a bitstream at a certain level, e.g., at a largest coding unit, a smallest coding unit, a prediction unit, etc.
Existing video encoding and decoding systems typically signal one set of filter parameters (e.g., one for each color component, Cb and Cr) at the picture layer. In other words, existing systems may signal a set of filter parameters for each color component, but use such set of filter parameters for the corresponding component in the entire picture. Because a picture (e.g., a large resolution picture, such as a 4K picture) may include several regions with different video content, specific filter parameters customized for each region of the picture could provide significant coding benefits. In such case, signaling only one set of filter parameters for an entire picture may not provide the best results and quality may suffer.
To improve quality and coding efficiency, it would be advantageous to provide a device and/or process that determines and signals specific filter parameters for individual regions of a picture, particularly for an inter-layer reference picture. Some advantages of the techniques disclosed herein relate to improving inter-component filtering coding efficiency and inter-layer reference picture quality by partitioning a picture into a quadtree structure having a plurality of leafs, and signaling specific filter parameters for each individual leaf such that parameters can vary between leafs.